Tropical Storm KATRINA (Text)

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TROPICAL STORM KATRINA DISCUSSION NUMBER 7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT THU AUG 25 2005
KATRINA IS GENERATING STRONG CONVECTION WITH TOPS COLDER THAN -80C.
HOWEVER...THE RADAR APPEARANCE HAS BEEN SOMEWHAT RAGGED...WITH THE
CENTER NEAR THE EDGE OF THE CONVECTION AND NO EVIDENCE OF THE EYE
STRUCTURE SEEN AROUND 00Z. RECENT DOPPLER RADAR DATA SHOWS THAT AN
INNER WIND CORE IS PRESENT...WHICH MAY BE THE SAME FEATURE SEEN IN
THE EARLIER RECONNAISSANCE FLIGHT. SATELLITE INTENSITY ESTIMATES
FROM ALL AGENCIES ARE 45 KT...SO THAT REMAINS THE INITIAL
INTENSITY.
THE INITIAL MOTION IS 275/7. KATRINA REMAINS SOUTH OF A COMPLEX
WEAKNESS IN THE SUBTROPICAL RIDGE. THE LOW LEVEL RIDGE HAS ONLY A
SLIGHT WEAKNESS...WITH THE ASSOCIATED FLOW TRYING TO PUSH KATRINA
TOWARD THE WEST-NORTHWEST. THE MID/UPPER-LEVEL RIDGE HAS A MORE
PRONOUNCED WEAKNESS ASSOCIATED WITH A TROUGH OVER THE EASTERN
UNITED STATES AND RIDGE ALONG THE GULF COAST. THE FLOW ASSOCIATED
WITH THESE FEATURES IS TRYING TO PUSH KATRINA TOWARD THE SOUTHWEST.
TRACK MODEL GUIDANCE RESPONDS TO THIS PATTERN WITH A SPREAD OF
LANDFALLS IN FLORIDA FROM THE KEYS TO NORTH OF LAKE OKEECHOBEE.
AFTER CROSSING FLORIDA...THE GUIDANCE HAS COME INTO SOMEWHAT BETTER
AGREEMENT THAT KATARINA WILL TURN NORTHWARD IN RESPONSE TO A
DEEPENING TROUGH OVER THE CENTRAL UNITED STATES...ALTHOUGH THERE IS
STILL A NOTABLE SPREAD. THE NEW FORECAST TRACK IS AN UPDATE OF THE
PREVIOUS PACKAGE AND IS DOWN THE MIDDLE OF THE ENVELOP OF MODEL
GUIDANCE.
KATRINA HAS BEEN BATTLING DRY AIR INTRUSION AND POSSIBLE NORTHERLY
SHEAR UNDERCUTTING THE OUTFLOW LAYER...WHICH HAS PREVENTED THE
CONVECTION FROM WRAPPING AROUND THE CENTER DURING THE NIGHT. SOME
NORTHERLY TO NORTHEASTERLY SHEAR WILL LIKELY CONTINUE UNTIL KATRINA
MAKES LANDFALL IN FLORIDA...WHICH WOULD SLOW DEVELOPMENT. ON THE
OTHER HAND...THE COLD TOPS AND THE INNER WIND CORE SUGGEST THE
POSSIBILITY OF STRENGTHENING. BASED ON THIS...THE INTENSITY
FORECAST CALLS FOR KATRINA TO BECOME A HURRICANE BEFORE LANDFALL.
KATRINA SHOULD WEAKEN WHILE SLOWLY CROSSING THE FLORIDA
PENINSULA...THE RE-INTENSIFY UNDER LIGHT SHEAR CONDITIONS OVER THE
GULF OF MEXICO.
FORECASTER BEVEN
FORECAST POSITIONS AND MAX WINDS
INITIAL 25/0900Z 26.2N 78.7W 45 KT
12HR VT 25/1800Z 26.2N 79.4W 55 KT
24HR VT 26/0600Z 26.3N 80.4W 65 KT...INLAND
36HR VT 26/1800Z 26.3N 81.4W 45 KT...INLAND
48HR VT 27/0600Z 26.5N 82.5W 40 KT...OVER WATER
72HR VT 28/0600Z 27.5N 84.0W 50 KT
96HR VT 29/0600Z 29.5N 85.0W 70 KT
120HR VT 30/0600Z 33.0N 83.0W 30 KT...INLAND
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